Oxidation resistance of SIC–AlN ceramics coated by oxidation-assisted-pack cementation process

Liquid-phase-pressureless-sintered SiC–AlN–Y2O3 composites were coated by means of modified pack cementation process (OXPAC, OXidation-assisted-PAck Cementation) using rare-earth oxides, RE2O3 (RE = Sc, Er, Sm, Lu, Ho), as reactive powders. The coatings, composed by the oxidation products of SiC, AlN and rare-earth silicates, were adherent to the substrate, without porosity and with a thickness of 10 μm. The oxidation resistance of the coated SiC–AlN–Y2O3 ceramics was also investigated at 1500 °C for a period of 200 h. The coated samples showed specific weight gain lower than the uncoated and pre-oxidised samples. Furthermore, the specific weight gain linearly increased with the rare-earth cationic radius.